class_docstr: A ``SpanField`` is a pair of inclusive, zero-indexed (start, end) indices into a
  :class:`~allennlp.data.fields.sequence_field.SequenceField`, used to represent a span of text.
  Because it's a pair of indices into a :class:`SequenceField`, we take one of those as input
  to make the span's dependence explicit and to validate that the span is well defined.
  
  Parameters
  ----------
  span_start : ``int``, required.
      The index of the start of the span in the :class:`SequenceField`.
  span_end : ``int``, required.
      The inclusive index of the end of the span in the :class:`SequenceField`.
  sequence_field : ``SequenceField``, required.
      A field containing the sequence that this ``SpanField`` is a span inside.
code: def as_tensor(self, padding_lengths, cuda_device=-1):
      # pylint: disable=unused-argument
      tensor = torch.LongTensor([self.span_start, self.span_end])
      return tensor if cuda_device == -1 else tensor.cuda(cuda_device)
  
file_path: magnitude/pymagnitude/third_party/allennlp/data/fields/span_field.py
imports: from __future__ import absolute_import
  import torch
  from allennlp.data.fields.field import Field
  from allennlp.data.fields.sequence_field import SequenceField
label_desc: Use image node_id 3 for calling the SpanField obj's underlying member method code with example usage: obj.as_tensor(padding_lengths, cuda_device) and returns: unknown